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In week 36, the majority of regions in Canada reported no influenza activity. Sporadic influenza activity was reported in 11 regions across five provinces and territories (YK, BC, AB, ON, and QC). For more details on a specific region, click on the map.
Figure 1 - Map of overall influenza/ILI activity level by province and territory, Canada, Week 36

Note: Influenza/ILI activity levels, as represented on this map, are assigned and reported by Provincial and Territorial Ministries of Health, based on laboratory confirmations, sentinel ILI rates and reported outbreaks. Please refer to detailed definitions at the end of the report. Maps from previous weeks, including any retrospective updates, are available in the mapping feature found in the Weekly Influenza Reports. Figure 1 - Text Description Laboratory Confirmed Influenza Detections

In week 35-36, the percentage of tests positive for influenza remained at interseasonal levels, ranging from 0.2% in week 35 to 0.7% in week 36. For data on other respiratory virus detections, see the Respiratory Virus Detections in Canada Report on the Public Health Agency of Canada (PHAC) website.
Figure 2 - Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, 2016-17
The shaded area indicates weeks where the positivity rate was at least 5% and a minimum of 15 positive tests were observed, signaling the start and end of seasonal influenza activity. Figure 2 - Text Description Nationally in weeks 35-36, there were 13 positive influenza tests reported. The detections of influenza A and B were approximately equal in weeks 35 and 36. The majority of regions across Canada reported no influenza detections. For more detailed weekly and cumulative influenza data, see the text descriptions for figures 2 and 3 or the Respiratory Virus Detections in Canada Report.
Figure 3 - Cumulative numbers of positive influenza specimens by type/subtype and province/territory, Canada, 2016-17 Figure 3 - Text Description To date this season, detailed information on age and type/subtype has been received for less than five cases.

Table 1 - Footnote 1 Table 1 includes specimens for which demographic information was reported. These represent a subset of all positive influenza cases reported. Cumulative data include updates to previous weeks.Return to Table 1 - Footnote1referrer
Table 1 - Footnote 2 Percentage of tests positive for sub-types of influenza A are a percentage of all influenza A detections.Return to Table 1 - Footnote2referrer
Table 1 - Footnote UnS Unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available. Specimens from NT, YT, and NU are sent to reference laboratories in other provinces.Return to Table 1 - FootnoteUnSreferrer

0

0

0

0

0

0

0

0

0

0

0

0%

0

0

0

0

<5

0

0

0

0

<5

<5

50%

0

0

0

0

0

0

0

0

0

0

0

0%

<5

0

0

<5

0

<5

0

0

<5

0

<5

50%

0

0

0

0

0

0

0

0

0

0

0

0%

<5

0

0

<5

<5

<5

0

0

<5

<5

<5

100%

50%

0%

0%

100%

50%

50%

0%

0%

100%

50%

-

-

Syndromic/Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 36, 0.98% of visits to healthcare professionals were due to ILI.
Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, 2016-17
Number of participants reporting in week 36: 82
Delays in the reporting of data may cause data to change retrospectively. In BC, AB, and SK, data are compiled by a provincial sentinel surveillance program for reporting to FluWatch. Not all sentinel physicians report every week. Figure 4 - Text Description

In weeks 35-36, no new laboratory confirmed influenza outbreaks were reported.
Figure 5 - Overall number of new laboratory-confirmed influenza outbreaksFigure 5 - Footnote1 by report week, Canada, 2016-17 Figure 5 - Footnote 1 All provinces and territories except NU report influenza outbreaks in long-term care facilities. All provinces and territories with the exception of NU and QC report outbreaks in hospitals. Outbreaks of influenza or influenza-like-illness in other facilities are reported to FluWatch but reporting varies between jurisdictions. Outbreak definitions are included at the end of this report.Return to Figure 5 - Footnote1referrer
Figure 5 - Text Description Provincial/Territorial Influenza Hospitalizations and Deaths

In weeks 35-36, less than five influenza-associated hospitalizations were reported by participating provinces and territoriesFootnote*.

0

0

0 (0%)

0

0%

0

0%

<5

0

<5 (100%)

0

0%

0

0%

0

0

0 (0%)

0

0%

0

0%

0

0

0 (0%)

0

0%

0

0%

0

0

0 (0%)

0

0%

0

0%

<5

0

<5 (100%)

0

0%

0

0%

Footnote * Note: Influenza-associated hospitalizations are not reported to PHAC by: BC, NU, and QC. Only hospitalizations that require intensive medical care are reported by SK. ICU admissions are not distinguished among hospital admissions reported from ON. It is important to note that the hospitalization or death does not have to be attributable to influenza, a positive laboratory test is sufficient for reporting.Return to footnote*referrerSentinel Hospital Influenza Surveillance

Pediatric Influenza Hospitalizations and Deaths

Surveillance of laboratory-confirmed influenza associated pediatric (≤16 years of age) hospitalizations from the IMPACT network has not yet begun for the 2016-17 season.Influenza Strain Characterizations

The National Microbiology Laboratory (NML) has not yet reported any influenza strain characterizations for the 2016-17 season.

"Safety and security don't just happen, they are the result of collective consensus and public investment. We owe our children, the most vulnerable citizens in our society, a life free of violence and fear." -Nelson Mandela

In week 52, a total of 18 regions in Canada reported no influenza activity. Sporadic influenza activity was reported in 19 regions across all provinces and territories except QC and SK. Localized activity was reported in 13 regions across four provinces (ON, SK, AB and BC). Widespread activity was reported in three regions (one each in SK, AB and BC). For more details on a specific region, click on the map.
Figure 1 - Map of overall influenza/ILI activity level by province and territory, Canada, Week 52

Note: Influenza/ILI activity levels, as represented on this map, are assigned and reported by Provincial and Territorial Ministries of Health, based on laboratory confirmations, sentinel ILI rates and reported outbreaks. Please refer to detailed definitions at the end of the report. Maps from previous weeks, including any retrospective updates, are available in the mapping feature found in the Weekly Influenza Reports. Figure 1 - Text Description Laboratory Confirmed Influenza Detections

The percentage of tests positive for influenza increased from 16% in week 51 to 24% in week 52. Compared to the previous influenza A(H3N2)-predominant season in 2014-15, the percent positive in week 52 (24%) was lower than the percent positive reported in week 52 of the 2014-15 season (34%). For data on other respiratory virus detections, see the Respiratory Virus Detections in Canada Report on the Public Health Agency of Canada (PHAC) website.
Figure 2 - Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, 2016-17, Weeks 51 & 52 The shaded area indicates weeks where the positivity rate was at least 5% and a minimum of 15 positive tests were observed, signalling the start and end of seasonal influenza activity.

Figure 2 - Text Description Nationally in week 52, 1,948 positive influenza tests were reported, up from 1,229 tests reported in week 51. To date, a total of 6,180 laboratory confirmed influenza detections have been reported. Influenza A(H3N2) is the most common subtype detected, representing 99% of subtyped influenza A detections (3812/3835). For more detailed weekly and cumulative influenza data, see the text descriptions for Figures 2 and 3 or the Respiratory Virus Detections in Canada Report.
Figure 3 - Cumulative numbers of positive influenza specimens by type/subtype and province/territory, Canada, 2016-17, Week 52 Figure 3 - Text Description To date this season, detailed information on age and type/subtype has been received for 5,008 laboratory confirmed influenza cases. Adults aged 65+ were the age group that accounted for the largest proportion of reported influenza cases (>45%) and the largest proportion of influenza A (H3N2) cases. Compared to the cases reported in the 2014-15 season at week 52, adults aged 65+ account for a smaller proportion of cases this season (approximately 45% in 2016-17 compared to 62% in 2014-15). Adults aged 45-64 account for a greater proportion of cases this season (approximately 23% in 2016-17 compared to 12% in 2014-15).

Table 1 - Footnote 1 Table 1 includes specimens for which demographic information was reported. These represent a subset of all positive influenza cases reported. Cumulative data include updates to previous weeks.Return to Table 1 - Footnote1referrer
Table 1 - Footnote 2 Percentage of tests positive for sub-types of influenza A are a percentage of all influenza A detections.Return to Table 1 - Footnote2referrer
Table 1 - Footnote UnS Unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available.
Specimens from NT, YT, and NU are sent to reference laboratories in the provinces.Return to Table 1 - FootnoteUnSreferrer
x Supressed to prevent residual disclosure

190

0

92

98

6

>359

<5

207

152

28

>387

x%

228

0

124

104

<5

>594

<5

430

164

21

>615

x%

325

0

190

135

<5

782

5

568

209

21

803

16%

>525

<5

273

252

9

1,147

8

678

461

19

1,166

23%

>1,056

<5

493

563

7

>2,011

<5

1207

804

20

>2,031

x%

2,327

<5

1,172

1,152

27

4,899

19

3,090

1,790

109

5,008

100%

99%

0%

50%

50%

1%

98%

0%

63%

37%

2%

Syndromic/Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 52, 3.4% of visits to healthcare professionals were due to ILI, up from week 51 where 2.0% of visits were due to ILI.
Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, 2016-17 Number of Sentinels Reporting Week 52: 60
Delays in the reporting of data may cause data to change retrospectively. In BC, AB, and SK, data are compiled by a provincial sentinel surveillance program for reporting to FluWatch. Not all sentinel physicians report every week. Figure 4 - Text Description Are you a primary healthcare practitioner (General Practitioner, Nurse Practitioner or Registered Nurse) interested in becoming a FluWatch sentinel?
Please visit our Influenza Sentinel page for more details.

Influenza Outbreak Surveillance

In week 52, 71 laboratory confirmed influenza outbreaks were reported: 49 in long-term care (LTC) facilities, five in hospitals and 17 in institutional or community settings. Of the outbreaks with known strains or subtypes: 57 outbreaks were due to influenza A of which 17 were due to influenza A(H3N2) (15 in LTC facilities and two in institutional or community settings), 40 were due to influenza A(UnS) (24 in LTC facilities, three in hospitals and 13 in institutional or community settings) and one was due to influenza B (in a LTC facility).
To date this season, 206 outbreaks have been reported and the majority (67%) have occurred in LTC facilities. In comparison at week 52 in the 2014-15 season, the previous influenza A(H3N2)-predominant season, 457 outbreaks were reported, of which 76% occurred in LTC facilities.
Figure 5 - Overall number of new laboratory-confirmed influenza outbreaksFigure 5 - Footnote1 by report week, Canada, 2016-17, Week 52 Figure 5 - Footnote 1 All provinces and territories except NU report influenza outbreaks in long-term care facilities. All provinces and territories with the exception of NU and QC report outbreaks in hospitals. Outbreaks of influenza or influenza-like-illness in other facilities are reported to FluWatch but reporting varies between jurisdictions. Outbreak definitions are included at the end of this report.Return to Figure 5 - Footnote1referrer
Figure 5 - Text Description Provincial/Territorial Influenza Hospitalizations and Deaths

In week 52, 185 influenza-associated hospitalizations were reported by participating provinces and territoriesFootnote*. Influenza A accounted for all but two of the reported hospitalizations. Adults aged 65+ accounted for the largest proportion of hospitalizations (72%).
To date this season, 892 hospitalizations have been reported, of which 98% were due to influenza A. Among cases for which the subtype of influenza A was reported, almost all (576/578) were influenza A(H3N2). Adults 65+ accounted for approximately 66% of the hospitalizations. Thirty-two intensive care unit (ICU) admissions and 20 deaths have been reported. The majority of deaths (80%) were reported in adults aged 65+ years.

In weeks 51 and 52, a total 48 laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network. All but one case was due to influenza A. The number of hospitalizations reported in week 51 and 52 were below the six-year average number of hospitalizations for those weeks.
To date this season, 117 laboratory-confirmed influenza-associated pediatric hospitalizations were reported by the IMPACT network. Children aged 0-2 years accounted for approximately 36% of hospitalizations. Influenza A accounted for 89% (n=104) of the reported hospitalizations, of which 53% (n=55) were influenza A(H3N2) and the remainder were A(UnS). Additionally, 18 intensive care unit (ICU) admissions have been reported, of which 67% were reported in children aged five years and older. No deaths have been reported this season.
Compared to 2014-15, the previous influenza A(H3N2)-predominant season, where 262 hospitalizations were reported as of week 52, there has been approximately half the number of cases reported to date in the current season.
Figure 6 - Cumulative numbers of pediatric hospitalizations (≤16 years of age) with influenza by type and age-group reported by the IMPACT network, Canada, 2016-17, Week 52 Figure 6 - Text Description Figure 7 - Number of pediatric (≤16 years of age) hospitalizations reported by IMPACT sentinel hospital network, by week, Canada, 2016-17, Weeks 51 & 52 The shaded area represents the maximum and minimum number of cases reported by week from seasons 2010-11 to 2015-16.
The number of hospitalizations reported through IMPACT represents a subset of all influenza-associated pediatric and adult hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.
Figure 7 - Text Description Adult Influenza Hospitalizations and Deaths

In weeks 51 and 52, a total of 151 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations were reported by the Canadian Immunization Research Network (CIRN). All but two cases were due to influenza A and the greatest proportion of cases (67%) occurred in adults aged 65+.
To date this season, 209 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations have been reported by CIRN. All but two hospitalized cases were due to influenza A. Adults aged 65+ accounted for approximately 68% of hospitalizations. To date, greater than nine ICU admissions and less than five deaths have been reported.
Figure 8 - Cumulative numbers of adult hospitalizations (≥20 years of age) with influenza by type and age-group reported by the CIRN network, Canada, 2016-17, Week 52 Figure 8 - Text Description Figure 9 - Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group (≥16 year of age), Canada 2015-16, Week 52 The number of hospitalizations reported through CIRN represents a subset of all influenza-associated adult hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.
Figure 9 - Text Description Influenza Strain Characterizations

During the 2016-17 influenza season, the National Microbiology Laboratory (NML) has characterized 199 influenza viruses [175 A(H3N2), 7 A(H1N1), 17 influenza B]. All but one influenza A virus (n=174) and 9 influenza B viruses characterized were antigentically or genetically similar to the vaccine strains included in both the trivalent and quadrivalent vaccines. Eight influenza B viruses were similar to the strain which is included only in the quadirvalent vaccine.

Viruses belonging to genetic group 3C.2a. A/Hong Kong/4801/2014-like virus belongs to genetic group 3C.2a and is the influenza A(H3N2) component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent vaccine.
Additionally, genetic characterization of the 62 influenza A (H3N2) viruses that underwent HI testing determined that 48 viruses belonged to genetic group 3C.2a and 10 viruses belonged to genetic group 3C.3a. Sequencing is pending for the remaining four isolates.The majority of viruses belonging to genetic group 3C.3a are inhibited by antisera raised against A/Hong Kong/4801/2014Table 3 - Footnote3.

"Safety and security don't just happen, they are the result of collective consensus and public investment. We owe our children, the most vulnerable citizens in our society, a life free of violence and fear." -Nelson Mandela

A total of 2,639 positive influenza detections were reported in week 1, an increase from the previous week. Influenza A(H3N2) continues to be the most common subtype detected.

One hundred and six confirmed influenza outbreaks were reported in week 1, with the majority occurring in long-term care facilities and due to influenza A(H3N2).

The number of hospitalizations, ICU admissions and deaths reported by participating provinces and territories sharply increased from week 52 to week 1; the majority of hospitalizations and all deaths reported in week 1 were in adults.

Influenza activity started early this season, but so far activity has been lower than the 2014-15 season when A(H3N2) was the predominant subtype.

In week 1, a total of six regions in Canada reported no influenza activity. Sporadic influenza activity was reported in 17 regions across eight provinces and territories. Localized activity was reported in 18 regions across nine provinces (PE, NS, ON, QC, MB, SK, AB, BC, and NU). Widespread activity was reported in eight regions (one region in QC,four regions in AB and three regions in BC). For more details on a specific region, click on the map.
Figure 1 - Map of overall influenza/ILI activity level by province and territory, Canada, week 1

Note: Influenza/ILI activity levels, as represented on this map, are assigned and reported by Provincial and Territorial Ministries of Health, based on laboratory confirmations, sentinel ILI rates and reported outbreaks. Please refer to detailed definitions at the end of the report. Maps from previous weeks, including any retrospective updates, are available in the mapping feature found in the Weekly Influenza Reports. Figure 1 - Text Description Laboratory Confirmed Influenza Detections

The percentage of tests positive for influenza increased from 23.5% in week 52 to 24% in week 1. Compared to the previous influenza A(H3N2)-predominant season in 2014-15, the percent positive in week 1 (24%) was lower than the percent positive reported in week 53 of the 2014-15 season (35%). For data on other respiratory virus detections, see the Respiratory Virus Detections in Canada Report on the Public Health Agency of Canada (PHAC) website.
Figure 2 - Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, 2016-17, Week 1 The shaded area indicates weeks where the positivity rate was at least 5% and a minimum of 15 positive tests were observed, signalling the start and end of seasonal influenza activity.

Figure 2 - Text Description Nationally in week 01, 2,727 positive influenza tests were reported, up from 1,948 tests reported in week 52. To date, a total of 8,976 laboratory confirmed influenza detections have been reported. Influenza A(H3N2) is the most common subtype detected, representing 99% of subtyped influenza A detections (5015/5039). For more detailed weekly and cumulative influenza data, see the text descriptions for Figures 2 and 3 or the Respiratory Virus Detections in Canada Report.
Figure 3 - Cumulative numbers of positive influenza specimens by type/subtype and province/territory, Canada, 2016-17, Week 1 Figure 3 - Text Description To date this season, detailed information on age and type/subtype has been received for 6,879 laboratory confirmed influenza cases. Adults aged 65+ were the age group that accounted for the largest proportion of reported influenza cases (>45%) and the largest proportion of influenza A (H3N2) cases. Compared to the cases reported in the 2014-15 season at week 53, adults aged 65+ account for a smaller proportion of cases this season (approximately 45% in 2016-17 compared to 62% in 2014-15). Adults aged 45-64 account for a greater proportion of cases this season (approximately 46% in 2016-17 compared to 63% in 2014-15).

Table 1 - Footnote 1 Table 1 includes specimens for which demographic information was reported. These represent a subset of all positive influenza cases reported. Cumulative data include updates to previous weeks.Return to Table 1 - Footnote1referrer
Table 1 - Footnote 2 Percentage of tests positive for sub-types of influenza A are a percentage of all influenza A detections.Return to Table 1 - Footnote2referrer
Table 1 - Footnote UnS Unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available.
Specimens from NT, YT, and NU are sent to reference laboratories in the provinces.Return to Table 1 - FootnoteUnSreferrer
x Supressed to prevent residual disclosure

132

0

36

96

<5

>537

<5

262

275

36

>573

x%

60

0

23

37

<5

>750

<5

485

265

27

>777

x%

197

0

70

127

<5

1,127

5

698

424

24

1,151

17%

248

0

81

167

<5

1,163

8

663

492

20

1,183

17%

877

0

182

695

8

>3,156

<5

1,495

1,661

33

>3,189

x%

1,514

0

392

1,122

22

6,739

19

3,603

3,117

140

6,879

100%

99%

0%

26%

74%

1%

98%

0%

53%

46%

2%

Syndromic/Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 1, 2.0% of visits to healthcare professionals were due to ILI, down from week 52 where 2.8% of visits were due to ILI.
Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, 2016-17 Number of Sentinels Reporting Week 1: 95
Delays in the reporting of data may cause data to change retrospectively. In BC, AB, and SK, data are compiled by a provincial sentinel surveillance program for reporting to FluWatch. Not all sentinel physicians report every week. Figure 4 - Text Description Are you a primary healthcare practitioner (General Practitioner, Nurse Practitioner or Registered Nurse) interested in becoming a FluWatch sentinel?
Please visit our Influenza Sentinel page for more details.

Influenza Outbreak Surveillance

In week 01, 106 laboratory confirmed influenza outbreaks were reported: 69 in long-term care (LTC) facilities, 15 in hospitals and 22 in institutional or community settings. Of the outbreaks with known strains or subtypes: 105 outbreaks were due to influenza A of which 24 were due to influenza A(H3N2) (four in hospitals, 11 in LTC facilities and nine in institutional or community settings), 81 were due to influenza A(UnS) (nine in hospitals, 51 in LTC facilities and 21 in institutional or community settings). One outbreak was due to influenza B.
To date this season, 333 outbreaks have been reported and the majority (68%) have occurred in LTC facilities. In comparison at week 53 in the 2014-15 season, the previous influenza A(H3N2)-predominant season, 623 outbreaks were reported, of which 74% occurred in LTC facilities.
Figure 5 - Overall number of new laboratory-confirmed influenza outbreaksFigure 5 - Footnote1 by report week, Canada, 2016-17, Week 1 Figure 5 - Footnote 1 All provinces and territories except NU report influenza outbreaks in long-term care facilities. All provinces and territories with the exception of NU and QC report outbreaks in hospitals. Outbreaks of influenza or influenza-like-illness in other facilities are reported to FluWatch but reporting varies between jurisdictions. Outbreak definitions are included at the end of this report.Return to Figure 5 - Footnote1referrer
Figure 5 - Text Description Provincial/Territorial Influenza Hospitalizations and Deaths

In week 1, 445 influenza-associated hospitalizations were reported by participating provinces and territoriesFootnote*. Influenza A accounted for all but three of the reported hospitalizations. A total of 15 ICU admissions and 13 deaths were reported in week 1. Adults aged 65+ accounted for the largest proportion of hospitalizations (75%). All deaths in week 1 were reported in adults.
To date this season, 1436 hospitalizations have been reported, of which 99% were due to influenza A. Among cases for which the subtype of influenza A was reported, almost all (858/861) were influenza A(H3N2). Adults 65+ accounted for approximately 69% of the hospitalizations. Sixty intensive care unit (ICU) admissions and 36 deaths have been reported. The majority of deaths (78%) were reported in adults aged 65+ years.

In week 01, a total of 46 laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network. All but one case was due to influenza A. The number of hospitalizations reported in week 1 is comparable to the number of hospitalizations reported for week 01 in the previous six seasons.
To date this season, 171 laboratory-confirmed influenza-associated pediatric hospitalizations were reported by the IMPACT network. Children aged 0-2 years accounted for approximately 41% of hospitalizations. Influenza A accounted for 92% (n=157) of the reported hospitalizations, of which 48% (n=75) were influenza A(H3N2) and the remainder were A(UnS). Additionally, 26 intensive care unit (ICU) admissions have been reported, of which the largest proportion (31%) was reported in children 10-16 years. No deaths have been reported this season.
Compared to 2014-15, the previous influenza A(H3N2)-predominant season, where 358 hospitalizations were reported as of week 53, there has been approximately half the number of cases reported to date in the current season.
Figure 6 - Cumulative numbers of pediatric hospitalizations (≤16 years of age) with influenza by type and age-group reported by the IMPACT network, Canada, 2016-17, Week 1 Figure 6 - Text Description Figure 7 - Number of pediatric (≤16 years of age) hospitalizations reported by IMPACT sentinel hospital network, by week, Canada, 2016-17, Week 1 The shaded area represents the maximum and minimum number of cases reported by week from seasons 2010-11 to 2015-16.
The number of hospitalizations reported through IMPACT represents a subset of all influenza-associated pediatric and adult hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.
Figure 7 - Text Description Adult Influenza Hospitalizations and Deaths

In week 1, a total of 171 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations were reported by the Canadian Immunization Research Network (CIRN). All but one case was due to influenza A and the greatest proportion of cases (82%) occurred in adults aged 65+.
To date this season, 375 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations have been reported by CIRN. All but three hospitalized cases were due to influenza A. Adults aged 65+ accounted for 75% of hospitalizations. To date, greater than eighteen ICU admissions and seven deaths have been reported.
Figure 8 - Cumulative numbers of adult hospitalizations (≥20 years of age) with influenza by type and age-group reported by the CIRN network, Canada, 2016-17, Week 1 Figure 8 - Text Description Figure 9 - Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group (≥16 year of age), Canada 2015-16, Week 1 The number of hospitalizations reported through CIRN represents a subset of all influenza-associated adult hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.
Figure 9 - Text Description Influenza Strain Characterizations

During the 2016-17 influenza season, the National Microbiology Laboratory (NML) has characterized 217 influenza viruses [189 A(H3N2), 10 A(H1N1), 18 influenza B]. All but one influenza A virus (n=198) and nine influenza B viruses characterized were antigentically or genetically similar to the vaccine strains included in both the trivalent and quadrivalent vaccines. Nine influenza B viruses were similar to the strain which is included only in the quadirvalent vaccine.

Viruses belonging to genetic group 3C.2a. A/Hong Kong/4801/2014-like virus belongs to genetic group 3C.2a and is the influenza A(H3N2) component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent vaccine.
Additionally, genetic characterization of the 62 influenza A (H3N2) viruses that underwent HI testing determined that 48 viruses belonged to genetic group 3C.2a and 10 viruses belonged to genetic group 3C.3a. Sequencing is pending for the remaining four isolates.The majority of viruses belonging to genetic group 3C.3a are inhibited by antisera raised against A/Hong Kong/4801/2014Table 3 - Footnote3.

During the 2016-17 season, the National Microbiology Laboratory (NML) has tested 224 influenza viruses for resistance to oseltamivir and zanamivir and 116 influenza viruses for resistance to amantadine. All viruses were sensitive to oseltamivir and zanamivir. All 116 influenza A viruses were resistant to amantadine (Table 4).

"Safety and security don't just happen, they are the result of collective consensus and public investment. We owe our children, the most vulnerable citizens in our society, a life free of violence and fear." -Nelson Mandela

Comment

In week 03, activity from several indicators including laboratory detections, outbreaks and hospitalizations declined from the previous week indicating that nationally the influenza season may have reached its peak in week 02.

A total of 2,667 positive influenza detections were reported in week 03, a decrease from the previous week.

A(H3N2) continues to be the most common type of influenza affecting Canadians.

The majority of cases, hospitalizations and deaths have been among adults aged 65+ years.

Sixty-six confirmed influenza outbreaks were reported in week 03, with the majority occurring in long-term care facilities and due to influenza A.

A total of 417 hospitalizations were reported by participating provinces and territories, down from 467 hospitalizations reported in the previous week.

In week 03, all but two reporting regions are reporting influenza or influenza-like illness activity. One region in NS and one region in NB reported no activity. Sporadic influenza activity was reported in 23 regions across ten provinces and territories. Localized activity was reported in twenty regions across seven provinces and territories. Widespread activity was reported in five provinces (three regions in AB, one region in ON, one region in QC, one region in PE and one region in BC). For more details on a specific region, click on the map.

Note: Influenza/ILI activity levels, as represented on this map, are assigned and reported by Provincial and Territorial Ministries of Health, based on laboratory confirmations, sentinel ILI rates and reported outbreaks. Please refer to detailed definitions at the end of the report. Maps from previous weeks, including any retrospective updates, are available in the mapping feature found in the Weekly Influenza Reports.
Figure 1 - Text Description Laboratory Confirmed Influenza Detections

The percentage of tests positive for influenza decreased from 27% in week 02 to 23% in week 03. This is an indication that we may have reached the peak in the percent positive and number of detections for influenza in week 02. In 2014-15, the previous influenza A(H3N2)-predominant season, the peak occurred in week 52 with 34% of tests positive for influenza. For data on other respiratory virus detections, see the Respiratory Virus Detections in Canada Report on the Public Health Agency of Canada (PHAC) website.

The shaded area indicates weeks where the positivity rate was at least 5% and a minimum of 15 positive tests were observed, signalling the start and end of seasonal influenza activity.
Figure 2 - Text Description
Nationally in week 03, 2,667 positive influenza tests were reported, down from 3,477 tests reported in week 02. To date, a total of 15,231 laboratory confirmed influenza detections have been reported, of which 98% have been influenza A. Influenza A(H3N2) is the most common subtype detected, representing over 99% of subtyped influenza A detections (8664/8703). For more detailed weekly and cumulative influenza data, see the text descriptions for Figures 2 and 3 or the Respiratory Virus Detections in Canada Report.

Figure 3 - Text Description
To date, detailed information on age and type/subtype has been received for 10, 808 laboratory confirmed influenza cases. Among cases with reported age and type/subtype information, adults aged 65+ accounted for over half of the reported influenza cases and the largest proportion (45%) of influenza A (H3N2) cases.

Table 1 - Footnote 1 Table 1 includes specimens for which demographic information was reported. These represent a subset of all positive influenza cases reported. Cumulative data include updates to previous weeks.Return to Table 1 - Footnote1referrer
Table 1 - Footnote 2 Percentage of tests positive for sub-types of influenza A are a percentage of all influenza A detections.Return to Table 1 - Footnote2referrer
Table 1 - Footnote UnS Unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available.
Specimens from NT, YT, and NU are sent to reference laboratories in the provinces.Return to Table 1 - FootnoteUnSreferrer
x Supressed to prevent residual disclosure

147

0

46

101

5

>844

<5

404

440

44

>888

x%

139

0

40

99

5

>1032

<5

593

439

37

>1069

x%

193

0

66

127

<5

>1661

<5

944

717

34

>1695

x%

248

0

94

154

9

1833

6

960

867

36

1869

17%

691

0

209

482

6

>5227

<5

2336

2891

52

>5279

x%

1418

0

455

963

>25

10605

14

5237

5354

203

10808

100%

98%

0%

32%

68%

2%

98%

0%

49%

50%

2%

Syndromic/Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 03, 2.1% of visits to healthcare professionals were due to influenza-like illness.

Number of Sentinels Reporting Week 03: 128 Delays in the reporting of data may cause data to change retrospectively. In BC, AB, and SK, data are compiled by a provincial sentinel surveillance program for reporting to FluWatch. Not all sentinel physicians report every week.
Figure 4 - Text Description
Are you a primary healthcare practitioner (General Practitioner, Nurse Practitioner or Registered Nurse) interested in becoming a FluWatch sentinel?
Please visit our Influenza Sentinel page for more details.

Influenza Outbreak Surveillance

In week 03, sixty-six laboratory confirmed influenza outbreaks were reported: 39 in long-term care (LTC) facilities, 19 in hospitals and 8 in institutional or community (other) settings. Of the outbreaks with known strains or subtypes, all outbreaks were due to influenza A, of which 17 were due to influenza A(H3N2) and 35 were due to influenza A(UnS).
To date this season, 536 outbreaks have been reported and the majority (68%) have occurred in LTC facilities. In comparison, at week 03 in the 2014-15 season, the previous influenza A(H3N2)-predominant season, 1,036 outbreaks were reported, of which 77% occurred in LTC facilities.

Figure 5 - Overall number of new laboratory-confirmed influenza outbreaksFigure 5 - Footnote1 by report week, Canada, 2016-17, Week 3 Figure 5 - Footnote 1 All provinces and territories except NU report influenza outbreaks in long-term care facilities. All provinces and territories with the exception of NU and QC report outbreaks in hospitals. Outbreaks of influenza or influenza-like-illness in other facilities are reported to FluWatch but reporting varies between jurisdictions. Outbreak definitions are included at the end of this report.Return to Figure 5 - Footnote1referrer
Figure 5 - Text Description Provincial/Territorial Influenza Hospitalizations and Deaths

In week 03, 417 influenza-associated hospitalizations were reported by participating provinces and territories*. Influenza A accounted for all but six reported hospitalizations. A total of ten intensive care unit (ICU) admissions and 24 deaths were reported in week 03. Adults aged 65+ accounted for the largest proportion of hospitalizations (69%). All ICU admissions and deaths in week 03 were reported in adults.
To date this season, 2,479 hospitalizations have been reported, of which 99% were due to influenza A. Among cases for which the subtype of influenza A was reported, almost all (1446/1450) were influenza A(H3N2). Adults 65+ accounted for 70% of the hospitalizations. Eighty-nine ICU admissions and 79 deaths have been reported. The majority of deaths (81%) were reported in adults aged 65+ years.

In week 03, 36 laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network. All but two cases were due to influenza A. The number of hospitalizations reported in week 03 is below the six year average for the same time period (Figure 7).
To date this season, 236 laboratory-confirmed influenza-associated pediatric hospitalizations were reported by the IMPACT network. Children aged 0-2 years accounted for approximately 41% of hospitalizations. Influenza A accounted for 93% (n=219) of the reported hospitalizations, of which 44% (n=96) were influenza A(H3N2) and the remainder were A(UnS). Additionally, 40 intensive care unit (ICU) admissions have been reported, of which the largest proportion (27%) was reported in children 10-16 years. A total of 25 ICU cases reported at least one underlying condition or comorbidity. No deaths have been reported this season.
In 2014-15, the previous influenza A(H3N2)-predominant season, there were 446 hospitalizations, 50 ICU admissions and three deaths reported as of week 03.

The shaded area represents the maximum and minimum number of cases reported by week from seasons 2010-11 to 2015-16.
The number of hospitalizations reported through IMPACT represents a subset of all influenza-associated pediatric and adult hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.
Figure 7 - Text Description Adult Influenza Hospitalizations and Deaths

In week 03, a total of 104 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations were reported by the Canadian Immunization Research Network (CIRN). All cases were due to influenza A and the greatest proportion of cases (74%) occurred in adults aged 65+.
To date this season, 607 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations have been reported by CIRN. All but four hospitalized cases were due to influenza A. Adults aged 65+ accounted for 78% of hospitalizations. To date, greater than 37 intensive care unit (ICU) admissions have been reported. A total of 26 ICU cases reported at least one underlying condition or comorbidity. A total of 12 deaths have been reported this season, all in adults aged 65+. The median age of reported deaths was 72 years.

The number of hospitalizations reported through CIRN represents a subset of all influenza-associated adult hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.
Figure 9 - Text Description Influenza Strain Characterizations

During the 2016-17 influenza season, the National Microbiology Laboratory (NML) has characterized 412 influenza viruses [372 A(H3N2), 10 A(H1N1), 30 influenza B]. All but one influenza A virus (n=371) and all (n=30) influenza B viruses characterized were antigentically or genetically similar to the vaccine strains included in both the trivalent and quadrivalent vaccines. Sixteen influenza B viruses were similar to the strain which is included only in the quadrivalent vaccine.

Viruses belonging to genetic group 3C.2a. A/Hong Kong/4801/2014-like virus belongs to genetic group 3C.2a and is the influenza A(H3N2) component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent vaccine.
Additionally, genetic characterization of the 132 influenza A (H3N2) viruses that underwent HI testing determined that 92 viruses belonged to genetic group 3C.2a and 21 viruses belonged to genetic group 3C.3a. Sequencing is pending for the remaining four isolates.The majority of viruses belonging to genetic group 3C.3a are inhibited by antisera raised against A/Hong Kong/4801/2014Table 3 - Footnote3.

During the 2016-17 season, the National Microbiology Laboratory (NML) has tested 313 influenza viruses for resistance to oseltamivir, 312 to zanamivir and 127 to amantadine. All viruses were sensitive to oseltamivir and zanamivir. All 127 influenza A viruses were resistant to amantadine (Table 4).

"Safety and security don't just happen, they are the result of collective consensus and public investment. We owe our children, the most vulnerable citizens in our society, a life free of violence and fear." -Nelson Mandela

In week 04, all but four regions (two in NL, and one each in NB and MB) are reporting influenza or influenza-like illness activity. Sporadic influenza activity was reported in 24 regions across thirteen provinces and territories. Localized activity was reported in 21 regions across six provinces. Widespread activity was reported in two provinces (two regions each in BC and AB). For more details on a specific region, click on the map.

Note: Influenza/ILI activity levels, as represented on this map, are assigned and reported by Provincial and Territorial Ministries of Health, based on laboratory confirmations, sentinel ILI rates and reported outbreaks. Please refer to detailed definitions at the end of the report. Maps from previous weeks, including any retrospective updates, are available in the mapping feature found in the Weekly Influenza Reports.
Figure 1 - Text Description Laboratory Confirmed Influenza Detections

In week 04, the percentage of tests positive for influenza remained similar to the previous week at 23%. For data on other respiratory virus detections, see the Respiratory Virus Detections in Canada Report on the Public Health Agency of Canada (PHAC) website.

The shaded area indicates weeks where the positivity rate was at least 5% and a minimum of 15 positive tests were observed, signalling the start and end of seasonal influenza activity.
Figure 2 - Text Description
Nationally in week 04, 2,586 positive influenza tests were reported, down from 2,667 tests reported in week 03. Many provinces and territories reported decreased influenza detections in week 04 but some regions such as the Atlantic region reported increased influenza detections from the previous week. To date, 17,914 laboratory confirmed influenza detections have been reported, of which 98% have been influenza A. Influenza A(H3N2) is the most common subtype detected, representing over 99% of subtyped influenza A detections (10038/10080). For more detailed weekly and cumulative influenza data, see the text descriptions for Figures 2 and 3 or the Respiratory Virus Detections in Canada Report.

Figure 3 - Text Description
To date, detailed information on age and type/subtype has been received for 12,694 laboratory confirmed influenza cases. Among cases with reported age and type/subtype information, adults aged 65+ accounted for almost half of the reported influenza cases and the largest proportion (45%) of influenza A (H3N2) cases.

Table 1 - Footnote 1 Table 1 includes specimens for which demographic information was reported. These represent a subset of all positive influenza cases reported. Cumulative data include updates to previous weeks.Return to Table 1 - Footnote1referrer
Table 1 - Footnote 2 Percentage of tests positive for sub-types of influenza A are a percentage of all influenza A detections.Return to Table 1 - Footnote2referrer
Table 1 - Footnote UnS Unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available.
Specimens from NT, YT, and NU are sent to reference laboratories in the provinces.Return to Table 1 - FootnoteUnSreferrer
x Supressed to prevent residual disclosure

140

0

41

99

<5

>1010

<5

465

545

47

>1057

x%

147

0

54

93

5

>1235

<5

682

553

41

>1276

x%

185

0

67

118

<5

1944

6

1079

859

38

1982

16%

191

0

69

122

7

2131

10

1100

1021

48

2179

17%

604

0

172

432

13

>6119

<5

2775

3344

74

>6193

x%

1267

0

403

864

29

12446

23

6101

6322

248

12694

100%

98%

0%

32%

68%

2%

98%

0%

49%

51%

2%

Syndromic/Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 04, 2.0% of visits to healthcare professionals were due to influenza-like illness.

Number of Sentinels Reporting Week 04: 108 Delays in the reporting of data may cause data to change retrospectively. In BC, AB, and SK, data are compiled by a provincial sentinel surveillance program for reporting to FluWatch. Not all sentinel physicians report every week.
Figure 4 - Text Description
Are you a primary healthcare practitioner (General Practitioner, Nurse Practitioner or Registered Nurse) interested in becoming a FluWatch sentinel?
Please visit our Influenza Sentinel page for more details.

Influenza Outbreak Surveillance

In week 04, 51 laboratory confirmed influenza outbreaks were reported: 35 in long-term care (LTC) facilities, eight in hospitals and eight in institutional or community (other) settings. All outbreaks were due to influenza A. Of the outbreaks with known strains or subtypes, seven were due to influenza A(H3N2) and 23 were due to influenza A(UnS). An additional three outbreaks due to ILI were reported in schools.
To date this season, 598 outbreaks have been reported and the majority (68%) have occurred in LTC facilities. Compared to the same period in the 2014-15 season, the previous influenza A(H3N2)-predominant season, 1,146 outbreaks were reported, of which 75% occurred in LTC facilities.

Figure 5 - Overall number of new laboratory-confirmed influenza outbreaksFigure 5 - Footnote1 by report week, Canada, 2016-17, week 4 Figure 5 - Footnote 1 All provinces and territories except NU report influenza outbreaks in long-term care facilities. All provinces and territories with the exception of NU and QC report outbreaks in hospitals. Outbreaks of influenza or influenza-like-illness in other facilities are reported to FluWatch but reporting varies between jurisdictions. Outbreak definitions are included at the end of this report.Return to Figure 5 - Footnote1referrer
Figure 5 - Text Description Provincial/Territorial Influenza Hospitalizations and Deaths

In week 04, 423 influenza-associated hospitalizations were reported by participating provinces and territories*. Influenza A accounted for the majority of hospitalizations (97%). Adults aged 65+ accounted for the largest proportion of hospitalizations (69%). A total of six intensive care unit (ICU) admissions and 24 deaths were reported in week 04.
To date this season, 2,964 hospitalizations have been reported, of which 99% were due to influenza A. Among cases for which the subtype of influenza A was reported, almost all (1692/1698) were influenza A(H3N2). Adults 65+ accounted for 70% of the hospitalizations. One hundred and one ICU admissions and greater than 105 deaths have been reported. The majority of deaths were reported in adults aged 65+ years.

In week 04, 31 laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network. All cases were due to influenza A. The number of hospitalizations reported in week 04 is below the six year average for the same time period (Figure 7).
To date this season, 270 laboratory-confirmed influenza-associated pediatric hospitalizations were reported by the IMPACT network. Children aged 0-23 months accounted for approximately 40% of hospitalizations. Influenza A accounted for 94% (n=253) of the reported hospitalizations, of which 45% (n=113) were influenza A(H3N2) and the remainder were A(UnS). Additionally, 45 intensive care unit (ICU) admissions have been reported, of which the largest proportion (29%) was reported in children 0-23 months. A total of 28 ICU cases reported at least one underlying condition or comorbidity. No deaths have been reported this season.
In 2014-15, the previous influenza A(H3N2)-predominant season, there were 467 hospitalizations, 53 ICU admissions and less than five deaths reported as of week 04.

The shaded area represents the maximum and minimum number of cases reported by week from seasons 2010-11 to 2015-16.
The number of hospitalizations reported through IMPACT represents a subset of all influenza-associated pediatric and adult hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.
Figure 7 - Text Description Adult Influenza Hospitalizations and Deaths

In week 04, 84 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations were reported by the Canadian Immunization Research Network (CIRN). All but one case were due to influenza A and the majority of cases (81%) occurred in adults aged 65+.
To date this season, 619 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations have been reported by CIRN. All but six hospitalized cases were due to influenza A. Adults aged 65+ accounted for 77% of hospitalizations. To date, greater than 30 intensive care unit (ICU) admissions have been reported. A total of 20 ICU cases reported at least one underlying condition or comorbidity. The median age of patients admitted to the ICU was 69 years. A total of 12 deaths have been reported this season, all in adults aged 65+. The median age of reported deaths was 82 years.

The number of hospitalizations reported through CIRN represents a subset of all influenza-associated adult hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.
Figure 9 - Text Description Influenza Strain Characterizations

During the 2016-17 influenza season, the National Microbiology Laboratory (NML) has characterized 459 influenza viruses [417 A(H3N2), 10 A(H1N1), 32 influenza B]. All but one influenza A virus (n=426) and all (n=32) influenza B viruses characterized were antigentically or genetically similar to the vaccine strains included in both the trivalent and quadrivalent vaccines. Seventeen influenza B viruses were similar to the strain which is included only in the quadrivalent vaccine.

Viruses belonging to genetic group 3C.2a. A/Hong Kong/4801/2014-like virus belongs to genetic group 3C.2a and is the influenza A(H3N2) component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent vaccine.
Additionally, genetic characterization of the 147 influenza A (H3N2) viruses that underwent HI testing determined that 112 viruses belonged to genetic group 3C.2a and 25 viruses belonged to genetic group 3C.3a. Sequencing is pending for the remaining 10 isolates. The majority of viruses belonging to genetic group 3C.3a are inhibited by antisera raised against A/Hong Kong/4801/2014Table 3 - Footnote3.

During the 2016-17 season, the National Microbiology Laboratory (NML) has tested 345 influenza viruses for resistance to oseltamivir, 344 to zanamivir and 132 to amantadine. All viruses were sensitive to oseltamivir and zanamivir. All 132 influenza A viruses were resistant to amantadine (Table 4).

"Safety and security don't just happen, they are the result of collective consensus and public investment. We owe our children, the most vulnerable citizens in our society, a life free of violence and fear." -Nelson Mandela

Comment

Influenza activity continues to be reported across Canada and two regions are reporting widespread influenza activity.

A slight increase in the percent of tests positive for influenza and number of laboratory confirmed influenza outbreaks was observed in week 5.

In week 05, 56 laboratory confirmed outbreaks were reported (up from 54 in the previous week), the majority in long-term care facilities and due to influenza A.

A(H3N2) continues to be the most common type of influenza affecting Canadians.

The majority of laboratory detections, hospitalizations and deaths have been among adults aged 65+ years.

A Canadian study reported an interim estimate of vaccine effectiveness of 42% against influenza A(H3N2) in Canada. The estimate is greater than the estimate for the previous A(H3N2) dominated season where no vaccine protection was found. The results of the study are consistent with expected vaccine effectiveness estimates for influenza A(H3N2). .

In week 05, all but two regions (one each in NB and MB) are reporting influenza or influenza-like illness activity. Sporadic influenza activity was reported in 24 regions across ten provinces and territories. Localized activity was reported in 24 regions across ten provinces. Widespread activity was reported in two provinces (one region each in BC and QC). For more details on a specific region, click on the map.

Note: Influenza/ILI activity levels, as represented on this map, are assigned and reported by Provincial and Territorial Ministries of Health, based on laboratory confirmations, sentinel ILI rates and reported outbreaks. Please refer to detailed definitions at the end of the report. Maps from previous weeks, including any retrospective updates, are available in the mapping feature found in the Weekly Influenza Reports.
Figure 1 - Text Description Laboratory Confirmed Influenza Detections

In week 05, the percentage of tests positive for influenza remained similar to the previous week from 23.5 to 24.3%. For data on other respiratory virus detections, see the Respiratory Virus Detections in Canada Report on the Public Health Agency of Canada (PHAC) website.

The shaded area indicates weeks where the positivity rate was at least 5% and a minimum of 15 positive tests were observed, signalling the start and end of seasonal influenza activity.
Figure 2 - Text Description
Nationally in week 05, 2,547 positive influenza tests were reported, fewer than the 2,586 tests reported in week 04. Western and Central-Eastern regions of Canada (BC, AB and ON) reported lower influenza detections in week 05 while a total of three provinces in the Central-Eastern and Atlantic regions of Canada reported higher influenza detections (QC, NB and NL). To date, 19,377 laboratory confirmed influenza detections have been reported, of which 98% have been influenza A. Influenza A(H3N2) is the most common subtype detected, representing over 99% of subtyped influenza A detections (10817/10866). For more detailed weekly and cumulative influenza data, see the text descriptions for Figures 2 and 3 or the Respiratory Virus Detections in Canada Report.

Figure 3 - Text Description
To date, detailed information on age and type/subtype has been received for over 14,347 laboratory confirmed influenza cases. Among cases with reported age and type/subtype information, almost half of the reported influenza cases and the largest proportion (47%) of influenza A (H3N2) cases were in adults aged 65+.

Table 1 - Footnote 1 Table 1 includes specimens for which demographic information was reported. These represent a subset of all positive influenza cases reported. Cumulative data include updates to previous weeks.Return to Table 1 - Footnote1referrer
Table 1 - Footnote 2 Percentage of tests positive for sub-types of influenza A are a percentage of all influenza A detections.Return to Table 1 - Footnote2referrer
Table 1 - Footnote UnS Unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available.
Specimens from NT, YT, and NU are sent to reference laboratories in the provinces.Return to Table 1 - FootnoteUnSreferrer
x Supressed to prevent residual disclosure

123

0

30

93

<5

>1150

<5

519

631

49

>1199

8%

136

0

37

99

<5

>1392

<5

745

647

44

>1436

10%

199

0

70

129

<5

>2175

<5

1199

976

40

>2215

15%

223

0

78

145

5

2395

6

1241

1148

53

2448

17%

632

0

191

441

8

>6967

<5

3256

3711

82

>7049

49%

1313

0

406

907

>13

>14079

15

6960

7113

268

>14347

100%

99%

0%

31%

69%

1%

98%

0%

49%

50%

2%

Syndromic/Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 05, 2.4% of visits to healthcare professionals were due to influenza-like illness, up slightly from 2.0% in the previous week.

Number of Sentinels Reporting Week 05: 118 Delays in the reporting of data may cause data to change retrospectively. In BC, AB, and SK, data are compiled by a provincial sentinel surveillance program for reporting to FluWatch. Not all sentinel physicians report every week.
Figure 4 - Text Description
Are you a primary healthcare practitioner (General Practitioner, Nurse Practitioner or Registered Nurse) interested in becoming a FluWatch sentinel?
Please visit our Influenza Sentinel page for more details.

Influenza Outbreak Surveillance

In week 05, 56 laboratory confirmed influenza outbreaks were reported, two more than the previous week: 32 in long-term care (LTC) facilities, 13 in hospitals and 11 in institutional or community (other) settings. All but one outbreak were due to influenza A. Of the outbreaks with known strains or subtypes, 12 were due to influenza A(H3N2) and 22 were due to influenza A(UnS). An additional four outbreaks due to ILI were reported in schools.
To date this season, 662 outbreaks have been reported and the majority (67%) have occurred in LTC facilities. Compared to the same period in the most recent previous A(H3N2) predominant season (2014-15), 1,225 outbreaks were reported, of which 74% occurred in LTC facilities.

Figure 5 - Overall number of new laboratory-confirmed influenza outbreaksFigure 5 - Footnote1 by report week, Canada, 2016-17, week 5 Figure 5 - Footnote 1 All provinces and territories except NU report influenza outbreaks in long-term care facilities. All provinces and territories with the exception of NU and QC report outbreaks in hospitals. Outbreaks of influenza or influenza-like-illness in other facilities are reported to FluWatch but reporting varies between jurisdictions. Outbreak definitions are included at the end of this report.Return to Figure 5 - Footnote1referrer
Figure 5 - Text Description Provincial/Territorial Influenza Hospitalizations and Deaths

In week 05, 336 influenza-associated hospitalizations were reported by participating provinces and territories, down from 423 reported in the previous week*. Influenza A accounted for nearly all of hospitalizations (99%). The largest proportion of hospitalizations (66% were among adults aged 65+. A total of six intensive care unit (ICU) admissions and 21 deaths were reported in week 05.
To date this season, 3,349 hospitalizations have been reported, of which 99% were due to influenza A. Among cases for which the subtype of influenza A was reported, almost all (1932/1947) were influenza A(H3N2). Adults 65+ accounted for 69% of the hospitalizations. One hundred and twelve ICU admissions and greater than 130 deaths have been reported. The majority of deaths were reported in adults aged 65+ years.

In week 05, 29 laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network. All cases but four were due to influenza A. The number of hospitalizations reported in week 04 is below the six year average for the same time period (Figure 7).
To date this season, 314 laboratory-confirmed influenza-associated pediatric hospitalizations were reported by the IMPACT network. Children aged 0-23 months accounted for approximately 40% of hospitalizations. Influenza A accounted for 93% (n=292) of the reported hospitalizations, of which 41% (n=119) were influenza A(H3N2) and the remainder were A(UnS). Additionally, 55 intensive care unit (ICU) admissions have been reported, of which the largest proportion (27%) was reported in children 0-23 months. A total of 36 ICU cases reported at least one underlying condition or comorbidity. No deaths have been reported this season.
In 2014-15, the previous influenza A(H3N2)-predominant season, there were 489 hospitalizations, 56 ICU admissions and less than five deaths reported as of week 05.

The shaded area represents the maximum and minimum number of cases reported by week from seasons 2010-11 to 2015-16.
The number of hospitalizations reported through IMPACT represents a subset of all influenza-associated pediatric and adult hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.
Figure 7 - Text Description Adult Influenza Hospitalizations and Deaths

In week 05, 109 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations were reported by the Canadian Immunization Research Network (CIRN). All but three cases were due to influenza A and the majority of cases (74%) occurred in adults aged 65+.
To date this season, 736 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations have been reported by CIRN. All but eight hospitalized cases were due to influenza A. Adults aged 65+ accounted for 77% of hospitalizations. To date, 39 intensive care unit (ICU) admissions have been reported. A total of 25 ICU cases reported at least one underlying condition or comorbidity. The median age of patients admitted to the ICU was 67 years. A total of 23 deaths have been reported this season, the majority in adults aged 65+. The median age of reported deaths was 82 years.

The number of hospitalizations reported through CIRN represents a subset of all influenza-associated adult hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.
Figure 9 - Text Description Influenza Strain Characterizations

During the 2016-17 influenza season, the National Microbiology Laboratory (NML) has characterized 560 influenza viruses [516 A(H3N2), 10 A(H1N1), 34 influenza B]. All but one influenza A virus (n=515) and all 34 influenza B viruses characterized were antigentically or genetically similar to the vaccine strains included in both the trivalent and quadrivalent vaccines. Nineteen influenza B viruses were similar to the strain which is included only in the quadrivalent vaccine.

Viruses belonging to genetic group 3C.2a. A/Hong Kong/4801/2014-like virus belongs to genetic group 3C.2a and is the influenza A(H3N2) component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent vaccine.
Additionally, genetic characterization of the XX influenza A (H3N2) viruses that underwent HI testing determined that XX viruses belonged to genetic group 3C.2a and XX viruses belonged to genetic group 3C.3a. Sequencing is pending for the remaining XX isolates. The majority of viruses belonging to genetic group 3C.3a are inhibited by antisera raised against A/Hong Kong/4801/2014Table 3 - Footnote3.

During the 2016-17 season, the National Microbiology Laboratory (NML) has tested 391 influenza viruses for resistance to oseltamivir, amantadine. All viruses were sensitive to oseltamivir and zanamivir. All 138 influenza A viruses were resistant to amantadine (Table 4).

"Safety and security don't just happen, they are the result of collective consensus and public investment. We owe our children, the most vulnerable citizens in our society, a life free of violence and fear." -Nelson Mandela

Comment

Overall, the slow decline in influenza activity in Canada has continued in week 11.However, many parts of Canada, particulary the Eastern and Atlantic regions are still reporting elevated activity in week 11.

In week 11, the number of laboratory detections, outbreaks and the number of geographic regions with influenza activity, decreased from the previous week.

Although adult sentinel hospitalizations decreased from the previous week, the number of hospitalizations and deaths reported by participating provinces and territories increased.

Influenza B detections and outbreaks in Canada are slowly increasing.

Although declining for most indicators, influenza A(H3N2) continues to be the most common subtype of influenza affecting Canadians.

The majority of laboratory detections, hospitalizations and deaths have been among adults aged 65+ years.

In week 11, one region in NL, reported no influenza or influenza-like illness activity. Sporadic influenza activity was reported in 29 regions across 11 provinces and territories. Localized activity was reported in 21 regions across nine provinces.No regions reported any widespread activity in week 11. For more details on a specific region, click on the map.

Note: Influenza/ILI activity levels, as represented on this map, are assigned and reported by Provincial and Territorial Ministries of Health, based on laboratory confirmations, sentinel ILI rates and reported outbreaks. Please refer to detailed definitions at the end of the report. Maps from previous weeks, including any retrospective updates, are available in the mapping feature found in the Weekly Influenza Reports.
Figure 1 - Text Description Laboratory Confirmed Influenza Detections

In week 11, the number (1,197) and the percentage of tests positive for influenza (16%) decreased from the previous week. Peak influenza detections occurred in week 02 at 27%. Although declining, influenza A continues to account for the majority of detections; however, influenza B detections have been steadily increasing for the past few weeks. Influenza B activity is very low compared to the same time period in the previous two seasons. For data on other respiratory virus detections, see the Respiratory Virus Detections in Canada Report on the Public Health Agency of Canada (PHAC) website.

The shaded area indicates weeks where the positivity rate was at least 5% and a minimum of 15 positive tests were observed, signalling the start and end of seasonal influenza activity.
Figure 2 - Text Description
To date this season, 32,836 laboratory confirmed influenza detections have been reported, of which 96% have been influenza A. Influenza A(H3N2) is the most common subtype detected. For more detailed weekly and cumulative influenza data, see the text descriptions for Figures 2 and 3 or the Respiratory Virus Detections in Canada Report.

Figure 3 - Text Description
To date, detailed information on age and type/subtype has been received for 23,013 laboratory-confirmed influenza cases (Table 1). Among cases with reported age and type/subtype information, adults aged 65+ accounted for almost half of the reported influenza cases. Among cases of influenza A(H3N2), adults aged 65+ represented 49% of cases, followed by adults aged 20-64 (34% of cases). In the previous influenza A(H3N2)-predominant season in 2014-15, adults aged 65+ represented 58% of cases and adults aged 20-64 represented 27% of cases.

Table 1 - Footnote 1 Table 1 includes specimens for which demographic information was reported. These represent a subset of all positive influenza cases reported. Cumulative data include updates to previous weeks.Return to Table 1 - Footnote1referrer
Table 1 - Footnote 2 Percentage of tests positive for sub-types of influenza A are a percentage of all influenza A detections.Return to Table 1 - Footnote2referrer
Table 1 - Footnote UnS Unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available.
Specimens from NT, YT, and NU are sent to reference laboratories in the provinces.Return to Table 1 - FootnoteUnSreferrer
x Supressed to prevent residual disclosure

>87

<5

10

77

7

2068

14

799

1255

102

2170

9%

>24

0

<5

24

21

2076

13

1038

1025

172

2248

10%

64

0

7

57

32

3233

27

1751

1455

177

3410

15%

85

0

17

68

19

3595

23

1871

1701

210

3805

17%

>321

<5

64

257

43

11063

13

5204

5846

317

11380

49%

586

<5

>98

483

122

22035

90

10663

11282

978

23013

100%

83%

x%

x%

82%

17%

96%

0%

48%

51%

4%

Syndromic/Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 11, 1.7% of visits to healthcare professionals were due to influenza-like illness, compared to 1.8% in the previous week.

Number of Sentinels Reporting Week 11: 101 Delays in the reporting of data may cause data to change retrospectively. In BC, AB, and SK, data are compiled by a provincial sentinel surveillance program for reporting to FluWatch. Not all sentinel physicians report every week.
Figure 4 - Text Description
Are you a primary healthcare practitioner (General Practitioner, Nurse Practitioner or Registered Nurse) interested in becoming a FluWatch sentinel?
Please visit our Influenza Sentinel page for more details.

Influenza Outbreak Surveillance

In week 11, 42 laboratory confirmed influenza outbreaks were reported (three less than the previous week). Among the reported outbreaks: 21 were in long-term care (LTC) facilities, seven in hospitals and 12 in institutional or community (other) settings. Of the outbreaks with known strains or subtypes, 11 were due to influenza A(H3N2), eight were due to influenza A(UnS) and seven outbreaks were due to influenza B. An additional two outbreaks due to ILI were reported in a school.
To date this season, 991 outbreaks have been reported and the majority (66%) have occurred in LTC facilities. Compared to the same period in the most recent previous A(H3N2) predominant season (2014-15), 1,552 outbreaks were reported, of which 74% occurred in LTC facilities.

Figure 5 - Overall number of new laboratory-confirmed influenza outbreaksFigure 5 - Footnote1 by report week, Canada, 2016-17, week 11 Figure 5 - Footnote 1 All provinces and territories except NU report influenza outbreaks in long-term care facilities. All provinces and territories with the exception of NU and QC report outbreaks in hospitals. Outbreaks of influenza or influenza-like-illness in other facilities are reported to FluWatch but reporting varies between jurisdictions. Outbreak definitions are included at the end of this report.Return to Figure 5 - Footnote1referrer
Figure 5 - Text Description Provincial/Territorial Influenza Hospitalizations and Deaths

In week 11, 261 influenza-associated hospitalizations were reported by participating provinces and territories, up from 254 reported in the previous week *. Influenza A accounted for 88% of hospitalizations. The weekly percentage of influenza B associated hospitalizations has been steadily increasing for the past few weeks (from 1.2% in week 02 to 11.5% in week 11). The largest proportion of hospitalizations were among adults aged 65+ years (71%). A total of ten intensive care unit (ICU) admissions were reported in week 11. An increase in the number of deaths was reported in week 11, with 35 deaths reported. All deaths were reported in adults aged 65+ years.
To date this season, 5,139 hospitalizations have been reported, of which 97% were due to influenza A. Among cases for which the subtype of influenza A was reported, almost all (2770/2787) were influenza A(H3N2). Adults 65+ accounted for 69% of the hospitalizations. A total of 193 ICU admissions and 277 deaths have been reported. The majority of deaths was reported in adults aged 65+ years.

* Note: Influenza-associated hospitalizations are not reported to PHAC by BC, NU, and QC. Only hospitalizations that require intensive medical care are reported by SK. ICU admissions are not distinguished among hospital admissions reported from ON. The hospitalization or death does not have to be attributable to influenza, a positive laboratory test is sufficient for reporting.
x Supressed to prevent residual disclosure

395

17

412 (8%)

11

6%

<5

x%

217

21

238 (5%)

13

7%

<5

x%

263

8

271 (5%)

18

9%

<5

x%

666

30

696 (14%)

52

27%

32

12%

3433

89

3522 (68%)

99

51%

238

86%

4974

165

5139 (100%)

193

100%

277

100%

Sentinel Hospital Influenza Surveillance

Pediatric Influenza Hospitalizations and Deaths

In week 11, 17 laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network. All but three cases were due to influenza A. The number of weekly hospitalizations reported since week 05 have been below the six year average for the same time period (Figure 7).
To date this season, 458 laboratory-confirmed influenza-associated pediatric hospitalizations were reported by the IMPACT network. Children aged 0-23 months accounted for approximately 39% of hospitalizations. Influenza A accounted for 91% (n=419) of the reported hospitalizations, of which 34% (n=141) were influenza A(H3N2) and the remainder were A(UnS). Additionally, 74 intensive care unit (ICU) admissions have been reported. Children aged 10-16 years accounted for 30% of ICU cases followed by children aged 0-23 months (27%). A total of 47 ICU cases reported at least one underlying condition or comorbidity. Less than five deaths have been reported this season.

The shaded area represents the maximum and minimum number of cases reported by week from seasons 2010-11 to 2015-16.
The number of hospitalizations reported through IMPACT represents a subset of all influenza-associated pediatric and adult hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.
Figure 7 - Text Description Adult Influenza Hospitalizations and Deaths

In week 11, 42 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations were reported by the Canadian Immunization Research Network (CIRN). All but nine cases were due to influenza A and the majority of cases (69%) occurred in adults aged 65+. The number of hospitalizations due to influenza B has been increasing since week 05.
To date this season, 1,222 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations have been reported by CIRN. Influenza A accounted for 98% of hospitalizations. Adults aged 65+ accounted for 78% of hospitalizations. To date, 81 intensive care unit (ICU) admissions have been reported. A total of 55 ICU cases reported at least one underlying condition or comorbidity. The median age of patients admitted to the ICU was 69 years. Approximately 51 deaths have been reported this season, the majority in adults aged 65+. The median age of reported deaths was 85 years.

The number of hospitalizations reported through CIRN represents a subset of all influenza-associated adult hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.
Figure 9 - Text Description Influenza Strain Characterizations

During the 2016-17 influenza season, the National Microbiology Laboratory (NML) has characterized 1,420 influenza viruses [1272 A(H3N2), 28 A(H1N1), 120 influenza B]. All but one influenza A virus (n=1271) and 40 influenza B viruses characterized were antigenically or genetically similar to the vaccine strains included in both the trivalent and quadrivalent vaccines. Eighty influenza B viruses were similar to the strain which is only included in the quadrivalent vaccine.
The World Health Organization (WHO) has released the recommended composition of the influenza vaccine for use in the 2017-2018 northern hemisphere influenza season. Trivalent vaccines are recommended to contain: 1) an A/Michigan/45/2015 (H1N1)pdm09-like virus; 2) an A/Hong Kong/4801/2014 (H3N2)-like virus; and 3) a B/Brisbane/60/2008-like virus (Victoria lineage). Quadrivalent vaccines are recommended to contain the above three viruses and a B/Phuket/3073/2013-like virus (Yamagata lineage).

Viruses belonging to genetic group 3C.2a. A/Hong Kong/4801/2014-like virus belongs to genetic group 3C.2a and is the influenza A(H3N2) component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent vaccine.
Additionally, genetic characterization of the 319 influenza A (H3N2) viruses that underwent HI testing determined that 272 viruses belonged to genetic group 3C.2a and 47 viruses belonged to genetic group 3C.3a. The majority of viruses belonging to genetic group 3C.3a are inhibited by antisera raised against A/Hong Kong/4801/2014Table 3 - Footnote3.

During the 2016-17 season, the National Microbiology Laboratory (NML) has tested 760 influenza viruses for resistance to oseltamivir and zanamivir and 180 influenza viruses for resistance to amantadine. All but one influenza A(H3N2) virus were sensitive to oseltamivir and all viruses were sensitive to zanamivir. All 180 influenza A viruses were resistant to amantadine (Table 4).

"Safety and security don't just happen, they are the result of collective consensus and public investment. We owe our children, the most vulnerable citizens in our society, a life free of violence and fear." -Nelson Mandela

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